Suspension Polymerization Of Styrene Research Articles

Poly(vinyl alcohol) as a stabilizer in the suspension polymerization of styrene: The effect of the molecular weight

The interfacial tension of the water-(PVA)/styrene system was measured as a function of the poly(vinyl alcohol) (PVA) concentration and temperature. Average size and particle-size distribution were obtained for a suspension of styrene in water using PVA as a stabilizer. We discuss the interfacial tension through the Zykonski equation to establish the behavior of the adsorption isotherms in unstirred systems and discuss the apparently contradictory results of the stirred experiment. We propose a simple configuration model that is congruent with both results. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 71–77, 1998

Hazards of Radical Polymerizations: Thermokinetic Investigation of Styrene Polymerization Methods.

Radical polymerization methods are prone to runaway under extreme process conditions. A review of case histories of polymerization incidents indicate that human error coupled with equipment failures, loss of cooling, temperature control and mischarging of reactants are the primary cause for triggering runaway accidents. Many of these accidents can be reduced or eliminated by changing the materials, alternative synthetic chemistry routes and process variables. Runaway hazard evaluation is the principle approach to assess and eliminate the inherent hazards. In this paper, hazard characterization of bulk and suspension methods of styrene polymerization, by microcalorimetric techniques is studied. The investigation indicates that suspension polymerization of styrene is less hazardous than the bulk polymerization method. The kinetics autocatalytic nature of suspension polymerization is presented. The coolant requirements for safe operation, as well as the temperature shoot up profiles for its failure for a typical 4000-kg batch commercial styrene polymerization reactor is simulated by employing reaction calorimetric data. ARC study indicates that a large excess of water present in the reaction mixture acts as a thermal sink and rules out the possibility of severe thermal hazards.

Scanning electron microscopy study of chlorosulfonated styrene-divinylbenzene macroporous resins

Macroporous copolymer beads were prepared by free radical suspension polymerization of styrene with divinylbenzene in presence of n-heptane and 2-ethyl-1-hexanol as diluent for the monomers. The copolymer particles were then sulfonated with a 40-wt% chlorosulfonic acid solution in dichloroethane at room temperature for 48 hours. The influence of the chlorosulfonation reaction on surface morphology of the beads was studied as function of diluent and divinylbenzene content. It was established that chlorosulfonation reaction led to the morphological changes in the macromolecular network prepared with 100% n-heptane, 100% 2-ethyl-l-hexanol for 20% DVB or with 30 and 40% DVB amount for 80 20 n-heptane/2-ethyl-l-hexanol.

Effect of double agitation on particle size in suspension polymerization of styrene with a loop reactor

AbstractSuspension polymerization of styrene was performed in the loop reactor. In order to allow wide change to the polymer particle size, a sub impeller was included within the main impeller. The sub impeller served to increase the fluid velocity and to uniformly disperse the polymer droplets during polymerization.It was investigated how the double agitation method by the main and the sub impellers affected the transient droplet diameter distribution and the final particle size distribution. The particle size could be changed widely by the double agitation method without the decrease in degree of the uniformity of the particle size.

Preparation of monodisperse microspheres using the Shirasu porous glass emulsification technique

Abstract Relatively uniform polymeric microspheres, with diameters ranging from 2.5 to 60 μm, and relative standard deviations of diameters close to 10%, were prepared by the ordinary suspension polymerization of either styrene(hydrophobic) or methyl methacrylate (MMA)-(more hydrophilic) based monomers. Unlike the conventional stirred-tank system, a particular microporous glass membrane (Shirasu porous glass; SPG) provided uniform monomer droplets continuously when monomer was allowed to permeate through the micropores under a carefully controlled nitrogen atmosphere. The monomer droplets, a mixture of monomers, diluents, oil-soluble initiator as well as water-insoluble reagent, were then suspended in the aqueous solution containing stabilizing agents, transferred to a stirred vessel, and polymerized. In the case of hydrophilic MMA spheres, the size distribution tends to become broader because hydrophilic substances easily wet the surface of SPG, leading to a permeation process which is uncontrollable. This difficulty was overcome by adopting the droplet swelling technique, in which the secondary emulsion droplets containing hydrophilic MMA were absorbed in the primary emulsion droplets consisting of hydrophobic components on the principle of the degradative diffusion process. Uniformity of the initial droplets is preserved during the swelling step, and subsequent polymerization. Applications of crosslinked microporous spheres were promising as packing beads for gel permeation chromatography and as carriers for enzyme immobilizations.

Tetraethyleneglycol diacrylate (TTEGDA)-crosslinked polystyrene resin as an efficient solid support for gel phase peptide synthesis

Various applications of the newly developed tetraethyleneglycol diacrylate (TTEGDA)-crosslinked polystyrene resin are illustrated by the synthesis of model peptides, fully protected peptides, peptide amides and biologically important sequences. PS-TTEGDA resin was prepared by suspension polymerization of styrene and TTEGDA and functionalized with chloromethyl, 4-cholromethyl-3-nitro, aminomethyl, α-bromopropionyl, a-aminopropionyl, 4-bromomethyl 3-nitrobenzamido, 4-aminomethyl-3-nitrobenzamido groups. Peptide synthesis was carried out using these modified resins by standard solid phase methodology. Coupling and deprotection in this synthetic strategy went to near completion showing the positive role of hydrophilic and flexible crosslinking agent TTEGDA in facilitating gelphase reactions. The peptides were removed from the support by photolysis, trifluoroaceticacid (TFA) treatment,trans-esterification or ammonolysis in high purity and yield. The crude peptides were purified by column chromatography/FPLC and characterized by aminoacid analysis, sequencing or1H-NMR.

Bulk and suspension polymerization of styrene in the presence of n‐pentane. An evaluation of monofunctional and bifunctional initiation

AbstractThe plasticizing effect of n‐pentane on the rate of bulk free radical polymerization of styrene and molecular weight distribution development has been modeled on the basis of the free volume theory for both monofunctional and bifunctional initiation. A strong decrease in the reaction rate in the late stages of the polymerization, due to the displacement of the onset of the gel effect, has been observed for both types of initiation. This decrease in the polymerization rate limited the terminal conversion to values well below 100% for mono‐functional initiation. However, in bifunctionally initiated polymerization, terminal conversions close to 100% were obtained in spite of the decrease in reaction rate. Contrary to what was expected, the molecular weight distribution obtained at terminal conversion was almost completely insensitive to these changes in polymerization rate. This phenomenon is explained in terms of limited transfer to monomer reactions when n‐pentane is present in the system. In suspension polymerization, the limiting conversion and plasticizing effects of n‐pentane in monofunctionally initiated systems, caused enhanced coalescence leading to suspension set‐up. In bifunctionally initiated systems this enhanced coalescence was completely overcome by the short duration of the particle growth stage, owing to high polymerization rates, and stable suspensions were achieved. For these systems the particle size distributions obtained were similar to that of suspension polystyrene without n‐pentane. © 1993 John Wiley & Sons, Inc.

Digital Simulation of Bulk and Suspension Polymerization of Styrene, Using Non-linear Regression for Curve Fitting the Kinetic Parameters

The original Chiu-Carrat-Soong (CCS) model for diffusion-controlled propagation and termination in free-radical polymerization is used to model conversion and average molecular weights histories in bulk or suspension styrene homopolymerization. Using the Marquardt method for non-linear regression, the key model parameters are fitted to literature available experimental data and the effect of important variables is simulated, obtaining agreement with the reported data and statistically significant models The numeri cal strategy for data fitting and problems encountered when doing so are explained.

Preparation and uranyl ion adsorptivity of macroreticular chelating resins containing phosphono groups

AbstractMacroreticular copolymer beads were prepared by suspension polymerization of styrene, bis(2‐chloroethyl) vinyl phosphonate (CEVP) and divinylbenzene (DVB) in the presence of toluene as diluent. The bis(2‐chloroethyl) phosphonate groups on the bead surface were converted into phosphono groups by hydrolysis with dilute nitric acid. For the additional enrichment of phosphono groups, the copolymers were phosphorylated at the phenyl rings with phosphorus trichloride in the presence of aluminum chloride and hydrolyzed and oxidized with dilute nitrics acid. The investigations on metal ion chelation characteristics of the bead‐type copolymers revealed that they have very high adsorptivity toward uranyl ions and good chemical resistance under acidic and alkaline media. It was also found that the phosphono group‐containing copolymer beads are effective adsorbents for other heavy metal ions such as Pb2+, Hg2+, Cd2+, and Cu2+.

A method for selecting a polyvinyl alcohol as stabilizer in suspension polymerization

Here we present a method for selecting a polyvinyl alcohol as stabilizing agent for the suspension polymerization of styrene, butyl acrylate or butyl methacrylate without carrying out the actual polymerization reaction. The stability of the non-reacting suspension is used to predict the stability of the same system when it is reacting. Our results indicate that for the concentration range examined, polyvinyl alcohols of moderate degree of hydrolysis (88%) and relatively large molecular weight (> 70 000) are the best suspension agents. Our findings can be extrapolated to the suspension polymerization of other monomers.

Study of suspension polymerization of styrene with a circular loop reactor

A circular loop reactor was devised and used to study the suspension polymerization of styrene. The transient droplet diameter distributions and the final particle size distributions were measured by changing the impeller diameter and the impeller speed. The effects of the impeller diameter on the size distributions and mean sizes of the final polymer particles were investigated. In the case of lower mixing power, the mean polymer droplet diameters depend upon impeller diameter in the early stage of polymerization, but become almost identical irrespective of the impeller diameter after the middle stage. In the case of higher mixing power, the mean polymer droplet diameters are almost identical irrespective of the impeller diameter throughout polymerization. The final mean particle sizes are correlated only with mixing power.

Characteristics of Particle Sizes produced by suspension polymerization of styrene

AbstractExperiments on the suspension polymerization of styrene were conducted at various stabilizer concentrations, dispersed phase hold‐up fractions, impeller types and impeller speeds. The experimental final particle size distributions obtained were almost always described by the upper limit number distribution. Plots of the maximum diameter, amax, and the mean diameters, a21 and a10, vs. the Sauter mean diameter, a32, gave straight lines with slopes of 1.24, 0.99 and 0.97, respectively.

In situ preparation of blends of polystyrene and poly (2,6-dimethyl-1,4-phenylene ether)

A new approach to prepare blends of polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene ether) (PPE) directly in the reactor is presented. The key step in this new route is the in situ ‘cold’ end-capping of PPE, dissolved in styrene, but the acetylation of the reactive phenolic end group of PPE. Without isolation of the PPE-acetyl (Ac), the reaction mixture is subjected to a classical styrene suspension polymerization procedure, yielding homogeneous beads of PS/PPE-Ac. The presence of PPE-Ac does not interfere chemically with the styrene polymerization as demonstrated by g.p.c. analysis of the separated constituents of the blend. A series of blends with different compositions was prepared. The maximum content of PPE in these reaction blends is 35 wt%, due to a limitation in viscosity of the PPE-styrene solution. Homogeneous transparent amorphous beads of PS/PPE-Ac were obtained, possessing a single glass transition temperature between 105°C and 140°C, depending on the composition.

Suspension polymerization of styrene with circular loop reactor

AbstractA circular loop reactor was devised and applied to the suspension polymerization of styrene. The transient droplet diameter distribution and the final particle size distribution are measured by changing widely the impeller speed, the dispersed phase volume fraction, and the stabilizer concentration. The effects of these conditions on the size distribution and mean size of the final polymer particle are investigated. An expression correlating the mean particle size with the operating conditions is derived. The circular loop reactor is found to be superior to the production of the polymer particle of uniform size.

On particle size distribution in suspension polymerization of styrene

Experiments were conducted on some of factors affecting the polymerized particle size distribution in suspension polymerization of styrene. Polymerization experiments with styrene at 80 °C showed that the final polystyrene product size distribution is strongly affected by the stabilizer concentration, the type and the speed of impeller, and the hold-up fraction.

Effect of sudden reduction of impeller speed on particle size distribution in suspension polymerization of styrene.

Effect of sudden reduction of impeller speed on particle size distribution in suspension polymerization of styrene.

Grafted chain as spacer for an insoluble polymer ligand. II. Two‐step polymerization using tetraethylthiuram disulfide as an initiator

AbstractIn order to increase the percent grafting in the graft polymerization of chloromethylstyrene onto a crosslinked polystyrene bead with UV light irradiation, a two‐step polymerization consisting of a suspension polymerization of styrene containing divinylbenzene using tetraethylthiuram disulfide as an initiator and then a subsequent graft polymerization of chloromethyl‐styrene onto the crosslinked polystyrene bead was carried out. The percent grafting of up to 180% was obtained, the value being about twofold larger than that for the usual method using benzoyl peroxide as an initiator. The higher percent grafting was found to result from the higher grafting efficiency due to the preferential decomposition of diethyldithiocarbamate group in the crosslinked polystyrene bead with UV light irradiation. The chloromethyl group in the grafted chain was converted to aminomethyl group, and then to the iminodiacetic acid group, which was a ligand group. The adsorption behavior of Cu(II) by the ligand polymer and the catalytic activity of the complex in the decomposition of hydrogen peroxide were examined, and both properties were found to be improved by introducing grafted chain as spacer, especially markedly at a higher percent grafting.

Dispersing behaviour of droplets in suspension polymerization of styrene in a loop reactor

AbstractSuspension polymerization of styrene was performed using a loop reactor. The dispersing behaviour of the droplets in the course of the reaction was observed. The mean droplet diameter was determined by the energy level at the impeller region. Moreover, the final particle size distribution and mean particle size were also determined after an elapsed time of 1‐2 hrs.An expression which correlated the final mean particle size with the operating conditions, such as the mixing conditions at the impeller region and the initial physical properties of the suspension system, was derived. The deposition of polymers on the reactor wall was found to be prevented due to the high fluid velocity.

Particle size distributions in suspension polymerization of styrene with a forward-reverse mixing method.

Suspension polymerization of styrene was performed with a forward-reverse mixing method. Size distributions and mean sizes of polymer particles formed under various operating conditions were measured.The results were compared with those obtained by conventional mixing and it was found that forward-reverse mixing gave polymer particles of more uniform size.

Hydrolysis of dextrin in the presence of sulfonated cross-linked polystyrene beads with grafted chain as spacer.

Polystyrene-grafted cross-linked polystyrene beads were prepared with a two-step polymerization, consisting of the first step; suspension polymerization of styrene containing small amount of divinyl benzene using tetraethylthiuram disulfide as an initiator, and the second step; polymerization of styrene onto the cross-linked polystyrene beads. Both percent grafting and grafting efficiency by this method were higher than those by conventional graft polymerization onto the beads using benzoyl peroxide as an initiator. In sulfonation by 1, 4-dioxane-sulfur trioxide adduct, the higher the percent grafting, the fewer sulfonic acid groups were introduced into the beads. Catalytic activity of the sulfonated beads on the hydrolysis of dextrin, however, increased with the increasing percent grafting, especially at the percent graftings higher than 200%. The catalyses followed ordinary second-order kinetics. The results showed that the increase in the catalytic activity with the increasing percent grafting was due to the effect of grafted chain as a spacer to separate the sulfonic acid group from the insoluble matrix.